You're not silly at all. I remember when my then DP and I had been together for a while, and we decided we both wanted kids. My parents were going through a messy divorce nad I couldn't face the whole family wedding thing.
So i came off the pill and was a couple of days late one month.
I remember so clearly going to buy the pregnancy test, a nd feeling so self conscious that Ihad no ring on.
As you say, I'm sure the checkout girl in Boots didn't give a stuff, but I felt so weird about it.
The test was negative, I went back on the pill, and soon later DH proposed. I conceived on our wedding night and we now have a 9 mth old ds.
I know things won't work out quite like this for you, but you really are not alone in feeling like this.
I think you should talk to your partner about this - I agree, maybe leave it a couple of weeks, one thing at a time and all that, but he needs to know how you feel.
i'm sure he will reassure you of his commitment to you and your baby, whether this results in an engagement of not.
And to echo what others have said, 9 months is a long time ( just think how long ago last November seems....)
I was stressing too about not knowing anything about babies, couldn't put a nappy on etc, but you will pick this up. Why not sign up for an NCT ( National Childbirth Trust) antenatal course? Probably a bit early yet, but don't leave it too long as they get very booked up, but they are great for giving you info about pregnancy, labour and the early days after your baby arrives. If you google NCT, you'll find it.
I also read loads of parenting books - it's not for everyone but made me feel more prepared and in control.
Good Luck with everything - I'm sure things will look brighter soon.